A laser printer (image forming apparatus) has a photosensitive member, a charger, and a developing device, and is configured such that a high voltage is applied to the charger and the developing device so as to perform a charging process and a developing process. In this type of image forming apparatus, reduction in the number of parts and reduction in the size of the apparatus are demanded, and various proposals are made heretofore. For example, Patent Document 1 describes a technique in which a developing voltage which is applied to a developing device is produced from a grid voltage which is applied to the grid of the charger, and a power supply for generating a developing voltage is removed.    [Patent Document 1] JP-A-H08-054768